The present invention relates to a suture manipulating implement, and particularly to a surgical instrument for manipulating a knotted suture to properly locate the knot thereof with respect to the tissue being sutured, and then for removing excess suture from the knot.
There is a growing demand to perform surgery, wherever possible, through small portals leading directly to the location operated on, thus minimizing damage to overlying and adjacent tissue. The technique is also known by the name endoscopy. Arthroscopy is the term used for the endoscopic approach applied to treat the various limb joints in the body.
As in all minimally invasive techniques, the area operated on is not exposed, and is not directly visible to the surgeon. The surgeon relies on a system of internal illumination and a small video camera. The camera projects an enlarged image onto a monitor screen to serve as a guide to the surgeon.
All necessary operations must be performed through a narrow opening. The size of this opening limits the size of the instruments used and the space available to manipulate them. In particular, access to tight joints is difficult. Small-size cutting, grasping, debriding and piercing instruments, capable of operating through small portals, have been developed for this purpose.
Suturing is also possible, and many suture passing and stitching devices are available to the arthroscopist. Tying a knot in situ is, however, barely possible.
The alternative solution is to use excess lengths of suture, and to bring the end of the strands to the outside for easy tying. One of several types of sliding knots, similar to the “hangman's knot”, is formed at the outside and then, aided by one of several types of knot manipulating instruments, is moved down the remaining strand through the access portal and is tightened firmly over the tissue stitched. The excess length of suture is now cut off a small distance above the knot.
It will thus be seen that the features desirable for such an arthroscopic suture cutter include: small diameter, ease of use, clean cutting, controlled distance of cut from the knot, and capability of accommodating sutures of different diameters and materials. The length of the suture end remaining after cutting is important: If it is too long, it may cause irritation; if it is too short, the knot may fail to hold. Ideally, the instrument should be able to handle and cut all types and sizes of suture material in use.
Insofar as we are aware, all instruments available on the market fail to include one or more of the above desirable features. One such device, which has been on the market since 1999 and offers several advantages over others, consists of a pair of loop handles, an elongated tube, and a solid shaft mounted within the tube. A bore sized to allow a suture to be threaded through it is formed through the distal end of the shaft at an angle to its axis. The cross-section of this bore is in the form of a droplet, and the angle relative to the axis of the shaft causes the exit to be much elongated in shape. The distal end face of the shaft is countersunk to define a recess to accommodate the knot. The shaft slides freely within a tubular cutter member in the form of a hardened tube, the distal end of which is ground into a sharp cutting edge. Sliding the tube forwardly relative to the shaft forces a suture threaded through the bore, irrespective of its thickness, against the narrow, tapered portion of the bore exit for clean cutting. The tube is advanced until it cuts the suture at a length determined by the distance between the distal end of the shaft and the bore exit.
In use, the surgeon threads the free end of the suture strand into the bore of the shaft, and then holds the end of the suture to tension it, while advancing the instrument along the suture strand until the knot is reached. A spring loaded safety latch in the handle prevents accidental premature cutting. Releasing the latch allows the surgeon to operate the movable handle for cutting the suture strand.
One drawback of the above device is that it is difficult to thread the suture through the bore, especially under the conditions prevailing in the operating room. Many surgeons, therefore, prefer to use other devices, such as suture scissors, where the suture remains free, thus sacrificing important advantages for easier use. Also, the practicable dimensions of the bore restrict the range of suture types for which the device can be used.
Another known implement of this type is described in our U.S. patent application Ser. No. 10/323,795, filed Dec. 20, 2002, and assigned to the same assignee as the present application. That implement, however, also includes a bore through which the suture is to be threaded, and therefore would have the same drawbacks as described above with respect to the device commercially available since 1999.